Conventional rotary extrusion blow molding apparatuses typically have a structural frame mounted on a rotating shaft. The structural frame has a plurality of molds mounted thereon and is known in the industry as a wheel. As the wheel is rotated, the plurality of molds is rotated past an extrusion die extruding a continuous parison. Each mold typically includes two mold halves, each comprising a mold cavity half therein, such that when the mold halves are closed, the mold defines a mold cavity corresponding to the configuration of the article to be molded, such as a container. Each mold, seriatim, is rotated past the extrusion die with the mold halves in an open configuration. The mold halves of each mold are then closed around the parison to enclose the parison within the mold defined by the mold halves. A blowing needle is then inserted into the parison within the closed mold and internal pressure is introduced to the parison, forcing it to inflate and conform to the configuration of the mold cavity. The molded object is then cooled and the mold opened to release the molded object from the mold.
When the two mold halves are clamped over one or more parisons prior to blowing of the parisons to form plastic containers, high clamp forces are required to close the mold halves on the parisons to pinch off the plastic and to hold the mold halves closed during blow molding. Conventional mold clamp assemblies are mounted on the frame of the machine supporting the assembly and, when actuated, transmit clamping force from a drive on one side of the mold to the other side of the mold through the frame. Alternatively, U.S. Pat. No. 7,611,657 discloses a mold clamp assembly for a rotary-type or shuttle-type blow molding machine. The clamp assembly is mounted on a frame and includes a mold opening and closing drive connected to the two mold halves independently of the frame, so that when the mold halves are closed, clamp forces are not transmitted to the mold halves through the frame.
Regardless of the transmission of forces, as the wheel is rotated, cam followers positioned on each mold engage a cam track. The cam followers follow the cam track, causing the cam followers to move laterally relative to the rotational movement of the wheel. The lateral movement of the cam followers controls the position of the mold halves and their movement between the open and closed positions.
The blow molding apparatuses described above are typically costly, heavy machines, which require a good deal of expertise to maintain. For example, when a mold clamp requires maintenance, the entire wheel must be taken off-line as the mold clamp is worked on. Currently, in order to perform maintenance or to change the molds, an operator/technician is positioned at the rear of the wheel, which is on the side opposed to the parison. In this position, the mold clamps and molds are generally presented to the operator/technician in a closed position. The wheel is stopped and the operator/technician must open the mold clamps in order to change to molds or to perform adjustments, repair or maintenance to the mold clamps. This requires a significant force to be applied to the mold clamp to overcome the clamp force. This force is currently applied by the use of a manually operated mold wrench.
Accordingly, there is a need for a device and improved method of opening and closing the mold clamp to perform maintenance and repair. In particular, there is a need to have a mold clamp opening/closing device which can automatically open and close the mold to facilitate the repair and maintenance of the mold clamps and allow for the molds to be changed more quickly and efficiently, thereby reducing the downtime of the molding apparatus, reducing the overall cost of the molding apparatus and lessening the impact to the operator or technician performing the repair and/or maintenance.